Abstract
As biominerals are good tracers of microbial interactions with the environment, they may provide signatures of microbial evolution and paleoenvironmental conditions. Since modern analogues of past environments help with defining proxies and biosignatures, we explored microbe mineral interactions in the water column of a maar lake, located in France: Lake Pavin. This lake is considered as a potential Precambrian ocean analogue, as it is ferruginous and meromictic, i.e., stratified with a superficial O2-rich layer (mixolimnion) and a deeper permanently anoxic layer (monimolimnion). We combined bulk chemical analyses of dissolved and particulate matter in combination with electron microscopy analyses of the particulate matter at different depths along the water column. The mineralogy changed along with water chemistry, and most of the minerals were intimately associated with microorganisms. Evolution of the redox conditions with depth leads to the successive precipitation of silica and carbonates, Mn-bearing, Fe-bearing and S-containing phases, with a predominance of phosphates in the monimolimnion. This scheme parallels the currently-assessed changes of microbial diversity with depth. The present results corroborate previous studies that suggested a strong influence of microbial activity on mineralogical diversity through extracellular and intracellular biomineralization. This paper reports detailed data on mineralogical profiles of the water column and encourages extended investigation of these processes.
Highlights
The major changes of the environmental conditions on the Earth’s surface over 4.5 billion years have driven a significant diversification of mineral species [1]
It would of interest investigate more deeply the minerals followed the evolution of the chemical composition of the water column, we suggest that speciation of Mn in the Mn-oxides and phosphates formed in the Lake Pavin water column, as well such textures from passive mineralthe deposition at diversity the surface of organicinvolved structures, as their fate inmay the arise sediment, and to explore microbial potentially ini.e., thethey
As the chemical composition of these minerals followed the evolution of the chemical composition of the water column, we suggest that such textures may arise from passive mineral deposition at the surface of organic structures, i.e., they would be the products of passive biomineralization [4,62]
Summary
The major changes of the environmental conditions on the Earth’s surface over 4.5 billion years have driven a significant diversification of mineral species [1]. Modern meromictic lakes studied so far were shown to host a diversity of microorganisms, especially with metabolisms involved in Fe and S biogeochemical cycles Such metabolisms may contribute to mineral formation through biomineralization processes:. Nitrate-dependent Fe(II)-oxidizing bacteria may be present in the water column of meromictic lakes, as suggested by electron and X-ray microscopy analyses of Lake Pavin samples [20] This metabolism has been shown to promote Fe-oxyhydroxide and Fe-phosphate precipitation, leading to bacterial cell encrustation [21,22,23]. The diversity of mineral phases and patterns across redox boundaries within the water column of meromictic lakes, as well as their connection with microbial activity remains poorly documented, such environments offer optimal conditions for sampling and studying neo-formed minerals. Whereas the seasonal variations of the chemistry and mineralogy are not explored in the present study, the potential relationships between the formed minerals and the activity of microorganisms is discussed as a basis for future in-depth studies of C, P, Fe and S biogeochemical cycles at this site
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
